Conducting thermoset polymers: a comparative study of Schiff base precursors with different end groups

Five different Schiff base monomers were used to form thermoset polymers by hot-melt processing. The study included three monomers with the same backbone structure but terminated with acetylene, vinyl or epoxy end groups, respectively, as well as two additional monomers with acetylene end groups but having different backbone structures. In this way we have compared the effect of the backbone and the crosslink structures on the electrical conductivities following p-type doping by molecular iodine. Two thermosets formed from acetylene-terminated monomers exhibited conductivities which were approximately a factor of ten higher than that measured in the thermosets formed from either vinyl- or epoxy-terminated monomers. The iodine dopant showed a non-Fickian Case II type of diffusion behavior in all thermosets. Electron spin resonance and optical spectroscopy showed evidence for the existence of polarons.